Most sources describe these names as indicating
a full-toned open flute with two mouths,
essentially an open Doppelflöte,
found at 8', 4' and 2' pitch.
Sumner dates it from the early 18th century; Williams mentions an
“open 8' or 4' Hohlflöte called
Jubalflöte at Görlitz (1697-1703) by E. Casparini who was
evidently not entirely familiar with current Saxon stop-names.”
Irwin claims it to be a synonym for
Seraphonflöte.
Adlung, however, maintains that these names are simply synonyms for
Octave.
The stop is named for Jubal, “the father of all such as handle the harp and organ”
(Genesis iv.21, KJV).